ABSTRACT Vector-borne pathogens such as Borrelia burgdorferi, the agent of Lyme disease, produce different proteins during infection of the mammalian host and the arthropod vector. These include distinct surface proteins to interact with the variety of tissues that are encountered. In addition, vector-borne bacteria must sense when thevectorisfeedingonahost,andefficientlycoordinatetransmissionprocesses. We discovered that several key infection-associated proteins that are produced during tick feeding and transmission can be induced in culture by increasing the rate of bacterial replication. A model proposes that this correspondstothedramatic increase in growth rate of B. burgdorferi whenatick begins tofeed onblood. We found that the master regulator of chromosomal replication, the DnaA protein, binds adjacent to the transcriptional promoters of loci that encode two global regulatory proteins. Both of those regulatory proteins directtheproductionofsurfaceproteinsthatcontributetomammalianinfectionprocesses.DnaAhomologsare known to regulate transcription in E. coli and other bacterial species. We hypothesize that DnaA serves to connectborrelialreplicationwithproductionofinfection-associatedproteins. The planned studies will critically test that hypothesis by identifying DnaA-binding sites throughout the B. burgdorferi genome by chromatin immunoprecipitation - sequencing (ChIP-Seq), characterizing new DnaA- regulatedloci,andbiochemicallydefiningfactorsinvolvedwithDnaA-binding. Altogether, results ofthese studies will characterizea novel regulon of theLyme diseasespirochete,providing substantialnewinsightonthebacteria?sphysiologyandinfectiousmechanisms.